What's the Scoop on Silicones?

We always get lots of questions about silicones, as they are in so many products and are of ongoing concern to many curly-haired consumers. I thought this month we could tackle a couple of those questions in a quick, practical manner (hopefully) to aid in the seemingly never-ending process of ingredient scrutiny and product selection.

Which Silicones are Water Soluble?

It is difficult to actually rank the silicones in order of water solubility, simply because they are usually either soluble or not. Most silicones are water insoluble due to being non-polar, but there are a few that are chemically modified in order to render them more compatible with water. The following table lists the main types of silicones found in hair care formulations. It also indicates whether or not they are water soluble and includes which surfactants can be used to ensure good removal of the silicone from the hair. Studies have found that the water-insoluble silicones show no appreciable buildup when a shampoo containing one of the recommended surfactants was used.

Why are Silicones Used in Hair Products?

Many currently available shampoos include silicones in the ingredient list. These additives act as conditioning agents, due to their ability to deposit onto the surface of the hair and form a film during the rinsing phase of the shampooing process.* This helps moisturize the hair by replacing oils stripped from the hair by the cleansing agents in the shampoo. Initially these were marketed as two-in-one products, but now they are found in a wide variety of products, especially as new properties are discovered, such as the ability of some silicones to enhance hair color retention. The inclusion of other oils in a shampoo can have a similarly moisturizing effect.

One interesting thing to note is that a published study in the Journal of Cosmetic science reports finding that the presence of cationic polymer (polyquaternium-10, in this study) significantly decreased the buildup of dimethicone on the hair over time.** The presence of these cationic polymers also enhances the deposition of the silicone onto the surface of the hair. Due to this synergy between the two types of ingredients, they will often be used together by formulators in shampoos.

Silicones offer many benefits, both to the hair care product formulator and the end-user. Careful reading of labels and understanding which silicones require occasional removal with surfactant-containing shampoos can allow the consumer to enjoy all of the good effects of silicones (softness, shine, better color retention, increased manageability), while suffering none of the ill effects of build-up.

Tonya McKay Becker is a curly-haired polymer scientist and cosmetic chemist whose academic and industrial research experience have provided her with expertise in the fundamentals and applications of polymer science and colloid chemistry. She has long had a fascination with the structure-property relationships of the complex solutions used in hair and skin care products, and how they interact with and impact these remarkable biological substrates.
Ever curious, Tonya has dedicated herself for more than a decade to honing her expertise on the science of curly hair, how it differs from straight hair, and how product ingredients used on curly hair affect its health and beauty. Her passion for sharing this knowledge with others has led to her current career of educating people from all backgrounds who share an interest in this exciting field.